99 Jeep Grand 4.0 - You know how when it's cold or you haven't driven the Jeep in a awhile it runs high rpm just until it's warmed up, then it idles down. I have a recent problem where it's running like this all the time, it never idles back down. Any thoughts on what this could be? It does not stall or sputter at all and the check engine light is not displayed, checked codes and nothing is displaying.

Thanks-

Sounds like a problem with the Idle Air Control Motor (IAC) They usually set an error code when they get flaky.
Taking it off and cleaning it sometimes works, but if not it needs to be replaced.
Disconnect the electrical harness to the IAC and idle the engine - it should change the idle rpms if it's working. It will also set a fault code when disconnected. If there is no change it's probably not the IAC.
A diagnosis can also be made by checking the voltage.